Metal cleaning method



April 14, 1953 FALER 2,635,064

METAL CLEANING METHOD Filed Jan. 8, 1952 MO LT'EN SALT BA 7 COOLING ZONE7 WATER Rmsa;

COLD wA-rse SUPPLY- 22 OVERF'LOW DRAIN- 25 IN V EN TOR.

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Patented Apr. 14, 1953 UNITED STATES OFFICE METAL CLEANING METHOD JohnA. Faler, Farmington, Mich., assignor to Kolene Corporation, Detroit,Mich.

1 Claim.

This application relates to the cleaning of metal and particularly tothe cleaning by molten salt baths.

Patent No. 2,458,661 describes a composition and process for-cleaning ofmetal by means of molten salt baths. The molten salt bath of that patentis of the alkali metal salt type, and the specific formula of thatpatent is as follows: 1.5-3.0 parts of sodium hydroxide, 1 part ofsodium nitrate, and 0.1-0.5 part of sodium chloride,

all by weight.

In the process of that patent, work pieces are first immersed in amolten salt bath of the above formula and thereafter immersed in a waterrinse bath and thereafter immersed in a subsequent oxide removal bath,such as a Weak acid bath. This application relates to that processgenerally, but introduces into the series of steps or baths, anadditional step and apparatus for such additional step which willhereafter be described upon reference to the following specification andto the appended drawing.

In such drawing the single figure diagrammatically illustrates apparatusfor cleaning of metal by the process of the aforesaid patent, assupplemented by the improvement of this application.

Referring to the drawing, it will be observed that at H! is shown amolten salt bathwhich may be of the character described in the aforesaidpatent. At II is shown a water rinse bath into which the work piecesemerging from the molten salt bath arejgenerally immersed for purposesof rinsing, with such water rinse bathbeing equipped with a conventionalcold water inlet and an overflow pipe leading to a drain for maintainingthe water rinse bath at a high enough level for complete immersion ofthe work pieces. 7

Above the baths l0 and II is shown a rail 12 along which rolls aconveyor M which suspends the work piece l5 and permits it to be loweredinto and lifted from the baths Band II. The apparatus thus far describedis conventional and has long been well known for employing the processof the aforesaid patent. We now proceed to a description of the novelmeans of this application.

Between the salt bath I0 and the rinse bath H is shown a cooling pool 20having a shallow pool 2| of cold water continuously running and suppliedfrom a cold water inlet 22 and maintained at constant low level by anoverflow pipe 23 leading to a drain. The sides of the tub or pool 20 arebuilt fairly high but the pool 2| may be extremely shallow,.just enoughto provide a shallow stream or pool of cold running water.

The functions of the tub 20 and the pool 2| are as follows. When a workpiece 15 is of extremely complex and large form as, for example, when itis a large and complex casting, such as a large diameter piston used indiesel engines, it has been discovered important to permit the castingto cool for quite a while before the casting is introduced into thewater rinse bath H after it leaves the molten salt bath it. During thecooling period, molten salt, dripping off the work piece 15, but for theprovision of the pool 2|, would form hard deposits in the area under thesuspended cooling work piece l5, and these hard deposits are extremelydifficult to remove. In addition, the drippings tend to splatter andbounce With consequent danger and messiness.

The provision of the tub 26 with its high walls and the shallow pool 2!as the location in which the work piece [5 is disposed during itscooling eliminates all these difficulties. The pool 2| of cold runningwater receives the molten salt drippings and dissolves such drippings,flushing them out in solution into the drain 23. Thus, there is noformation of hard deposits of the salt dripping from the work piece.Likewise, there is no bouncing and splattering of the drippings, becauseas the drippings drop into the pool 2| they are immediately dissolved.The side walls of the tub 20 prevent any splattering that might takeplace but are really not necessary, since all, or practically all, ofthe molten salt will drip downwards from the work piece into the pool 2|and are there dissolved and carried off to the drain 23.

Now having described the apparatus and process hereof, reference shouldbe had to the claim which follows.

I claim:

In a metal cleaning process, the steps of immersing a work piece in amolten alkali metal salt bath, thereafter suspending the hot work piece,dripping wet with molten salt, above a shallow pool of running water,and thereafter immersing the cooled work piece, from which much of themolten salt has dripped off, into a water rinse bath.

' JOHN A. FALER.

References Cited in the file of this patent Tainton Feb. 16, 1943

